Large gaseous fuel engines are often operated at injection timings which are less than optimum and with the output power from each of the cylinders relative to the others unbalanced. Obtaining control over injection timing and power balancing to operate gaseous fuel engines at optimum settings has been a problem.
Many large gaseous fuel engines do not operate at optimum settings because the fuel injection valves in these engines are operated by mechanical cam-driven valve trains. In these engines, the injection timing and the duration each valve is held open is fixed by the cam's profile and the cam's phase relationship to the engine's crankshaft. Although the start of the injection timing and the duration of the injection with a mechanical cam-driven valve train can be varied, the modifications required are complex and are often less than ideal.
Other engines do not operate at optimum settings because they fail to take into account or do not address the variety of factors, including engine operating conditions and engine usage, which can affect the desired time to start the injection of fuel for each cylinder. For example, in a gaseous fuel two-stroke engine, the injection timing should be set to start at a time which will minimize the amount of fuel which could escape through the exhaust port. Additionally, the injection timing should be adjusted to maximize time for fuel and air to mix. For example, direct cylinder fuel injection applied to liquid fuel two-stroke engines requires that the liquid fuel be given time to vaporize in the cylinder. To accomplish this, liquid fuel engines typically have fuel injection timing advanced for starting only. However, with fuels which are injected into the cylinders in the gaseous state, the time at which the injection of fuel is to start does not need to be advanced because when the gaseous fuel enters the cylinder it is ready for combustion.
In addition to problems with injection timing, balancing the power output between cylinders in an engine has also posed a challenge. Typically, power balancing has been accomplished manually by adjusting the throttle valve for each cylinder in the engine until the power output by each cylinder is about equal. Although these manual adjustments are reasonably effective, they are time consuming and must be redone each time the operating conditions for the engine change.
Accordingly, there is a need for an injection timing and power balancing control in a two-stroke, gaseous fuel engine.